1. Field of the Invention
The present invention relates to a strained quantum well structure and an optical device including such a strained quantum well structure, such as a semiconductor laser or a wavelength filter.
2. Description of Related Background Art
Semiconductor lasers, which output a transverse magnetic (TM) polarized beam, have been known. Such lasers have active layers including strained quantum well structures into whose quantum wells a tensile strain is introduced.
In a conventional semiconductor laser, once a strained quantum well structure has been formed, it is impossible to change the polarization direction of its light oscillation because its energy band structure is fixed.